Brake



June 17., 1941.` w

T. P; CHASE 2,246,242

BRAKE Filed Sept. 16, 1939 :s sheets-sheet 1 -n-lilllm v1. .A

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Bg u v l g a' v Gttoregs June 17, 1941. T, P, CHASE 2,245,242

BRAKE I 'Filed sept. 1e, l19:49 s sheets-sheet 2 zf a/ v5 75 75 N; 5l a5:Tg y67 l Y 69' g; f 77. el 55' T; 2/ [kse I 65 l 15 ,if 7"/ j Z////54g. 5

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BRAKE Filed Sept. 16, 1939 3`Sheets-Sheet3 /rlllllllllllfllllq 111Patented June 17, 1941 eral Motors Corporation, Detroit, Mich.,acorporation of Delaware Application september 1s, 1939, sei-lai No.298,205 4 Claims. (ci. iss-isz) This invention relates to frictionbrakes and 1s the result of eiorts to improve a brake of the kind havingan assembly of shoes adapted to be spready into engagement with vtheange of a rotating drum.

The object of the invention is to providev ashoe assembly such that eachshoe is self-energized by the drum for each directionof' rotationwhereby the greatest possible advantage may be taken of the energizingeffect of the rotating drum-therebyY minimizing the manual eiortrequired to apply the brakes; so to arrange the spreading and an-4choring mechanismv that the effective braking action of the shoes shallbe substantially equalized y for each direction of drum rotation to theend of equalzing the wear of the friction 'faclngs and to avoid drumdistortion; and to produce this equalized action by a servo eieot of oneshoe upon the other in each direction of drum rotation without the needfor a duplication of 'applying vmeans whereby the construction maybecomparatively simple and inexpensive.

As anotherr object the invention aims to accomplish the major objectwith shoes so constructed f as to employ the well-known articulatinglink anchorage.

The accompanying drawings show embodiments of the invention.

In the drawings:

Figure 1 is a transverse section through the flange of a drum showingthe shoe assembly in elevation.

Figure 2 is a section on line 2-2 of Fig. 1.

Figure 3 is a section on 3-3 Figure 1.l

Figure 4 is a view in elevation as seen from line 4--4 of Figure 3.

Figure 5 is a section on line 5-5 of Figure l.

Figure 6 is a section on line 6-6 of Figure l.

Figure 7 is a transverse section through the lower part of a drum flangeshowing a modiiied form.

Figure 8 is a section on line 8 8 oi' Figure 7.

Figure 9 is a transverse section through the lower part of the flange ofa drum showing another modication.

Figure l0 is a section o n line lil-|0701 Figure 9.

Figure l1 is a transverse section through the upper part of the flangeof a drum showing a modified form.

Figure 12 is a section on line I2-I2' of Figure il.

Referring to Figures 1 to 6, numeral il is used to designate a brakedrum. It will be understood that in the environment for which theinvention is more particularly intended, one such drum will be carriedby each vehicle wheel. Mounted ad- Amitted to the `rear axlehousing'orl't'ofthe 'fron ,g1 steering knuckle as the caseimayflbe; 24"Ihere may "cover at .IL transmits the tordueft'o. the ""cover'. Asshownon the drawing-'s there are twdshoes'u I9 and .2l having websI9'andfzi'zaand'flanges jacent `the but not forirotatinji-s''a coverplate I3 which also serves as the mediumthrough which the braketorquefroxnlthe shoes 'fis trans be a torque plate I5 betweerithebottoniifo'ffthel-` drum and the drum -cover as shown in/iiguresijf and3.k When sucha .torqueplat isus'ed''i't'takes I' the torqueidiruectlyand,f'bein'g fastenedto-`thef provided with friction Ia'cings 23 tonange of the drumjas usual.

The objects, of thisiinvention `are'attainfedby the use` of a ysinglemotory unit. 'This' ismarkedfiv" and is secured to` the vcover 'between'on'epati'rf'oi adjacent ends Yof the shoes. 'The 'motor 'unit' l shownis the so-calledlwheel-cylinder-"oiga con-l ventional hydraulic system.:It includes a cylinder 2, two pistons 29 and-29v each provided with asealing cup 3|. Fluid frornthe master'cylinder is admitted to the spacebetween the. two pistons.

Between the two pistonsis a spring 33 to hold the cups 3| against thepistons.. At `vone end ofthe cylinder. Threaded to the disk 35 is aplunger 39 having a forked end engagingthe web I9. The other piston 29'has asocket 4I to receive the f rounded end 43 of a link 45 pivoted' toshoe 2| at 4l. The link is formed from two plates' 45 and 45" of whichplate 45'? continues beyond the pivot 4l and carries a pin 49 extendingthrough a somewhat enlarged opening "5I, in the` web 2|'. A spring 53surrounds the pin and presses the plate 45'A frictionally against theweb 2 I By this construction the angular relation between the shoe andthe link 45 may vary to `obtain the`most eiective irictional engagementbetween the shoe and the drum flange without the occurrence of undesiredrotation of the links at 4l. A spring 55 is terminally connected to theshoes I9 and 2l to bias the assembly to its released position. Othersprings 5l and 59 connect the shoes tothe torque plate, these springsvbeing located near the other pair of shoe ends. It will be noted-that bythe rotation of disk 35 adjustment is provided to accommodate the liningwear of kshoe I9. 'I'he disk 35 by its engagement with the end ofcylinder 21 limits the release movement of the shoe toward the cylinderwhereby the cylinder becomes a torque receiving abutment. In a similarway piston 279' has an annular ange 29 which may .so applied to the linkpin 1I engaging the end of slot el and apart actsfss aservo force `to'apply'l shoe i! which, 75

engage the end of cylinder 21 for a like purpose. Torque plate il hasthree elongated openings in the region adjacent the pair of shoe endsrelmote from cylinder 21. These are radially spaced and are marked Il.Il and Il respectively. A 5

pin l1 extend'sthrough Il. Onthesides of torque plate il are links Il.It supported on pin t1. Rotatably supported by links II' are pins 1| and13 which pass through torque plate openings Il and II respectively.Other l0 slots 11 and 1I. the registering slots 11 openl5 ing towardshoe I while the slots ll open toward shoe 2l. Retainer plates Il, Il'arealso carried by pins l1 and 18. 'Ihese plates cover the slots and areheld in piace by the heads of the pins and by fastening means such assnap rings Il. The several links and plates constitute a lever operablefor a purpose to be explained.

A pair of plates Il, Il' form an articulating link for shoe II. Theseplates lie on opposite sides oi' the web of the shoe and are pivoted. 25thereto by a pin l1. Near the end of the shoe is a spring devicecomprising a spring surrounding a pin Il, the device functioning topermit a limited swinging of the linkageresisted when so applied, isadditionally energised by the rotating drum. This reverstbilityin actionis made possible by the oating support of the 'lever between the shoes.The specific structure of this lever is of importance. It thearticulating llnksattheendsoftheshoesweretoengaga the links 1l and 1l'at distances from the-ad- Jacentpinsgreaterthantheradiusofthesepins thepins would obviously need a greater spacing than in the arrangement toobtain the desired leverage. By the arrangement illustrated it ispossible to secure the desired ratio of leverarmswithalevernottoogreatinlengthtobe installed in the conventionalbrake. It will be seen from Figure 3 andligure that the linkage ss.ss'straddles the end 'orpln 1| at adistance from its axis intersects thelinkage thecenteroi'pinli lessthantheradiusthereof. This is madepossible by the association of links Il and 1l. In the'case of linkagel2 the forks also 'engage links 18,15' but engge the links in the planeof the reduoedparts 1I.; oi the pin 1I and in this case. the samerelatbnprevails relative to the radius of the pinll.

Inl'lgures'l andisshownaseeon'dandsimplined form which, being simpler.may be regarded as apreferred embodiment.' Inthese the drum is markedlli and numerals iis and I2I- designatethe shoes. 'Ihe backing piateviiby friction between the web and the linkage.l The so is vformed as iinFigure 8 andan anchor plate ill'at its is shaped as shown by ends ci'link It and Il' are tapered and seat in'- the dared slots 11 as bestshown by Figure 4, Similarly seated in slots 1l are the furcations of athrust member l2." A stem Il is seated in 'an opeling of member l2. Itis provided with a notched annulus Il and its other endis threadedtoengage a threaded openingll in a link II pivoted to the web 2i' of shoe2| at lli.

When the vehicle is at restand the brake not applied. the springs sl, s1and ls hold the mL shoes `away from the drum. Disk II and flange 20"vdetermine the release position at the wheel cylinder end of the shoesand the end walls of slots I8 and Il determine the correspondingposition at the other ends of the shoes. The forces 5- exerted by springl1 and II are applied to the iioating link means 1I and 15' constitute acouplel to hold the parts in the position shown in Figure l. If thebrake is applied while the vehicle is standing the linkage Il., 8l' forone shoe 50 .and l2 for the other constitute the anchoring means and thetwo shoes are spread apart each being equally eii'ective to holdthe caragainst rolling.` If on the other hand the vehicle is moving and thedrum rotating counterclockwise (Figure 1-) the pressure applied aty 39to shoe il` is supplemented bythe self-energizing eirect upon shoe Ilnfthe rotating drum. The engagement of pin 1lwith thewall of theislot'takes one Figure '1. plate H1 is' welded to the cover plate lil. Itqhol an axial-'aange Il! provided with an'elansated'openmg m. Theopenonevmarginalwali bent up as at' |23.

A pivot piaf-III is mountedfinvthe cover plate c lili and the lowerportionV ofv the anchor yplate notched as at 4III on 1 notch are engagedby the furcations at-the' e`nd of a link l0.v Thelink" includes anint`e'rnally,"""` threaded socket I4I,'a stem il] threaded there-v in,the stem having .vnotehedrmg m 'and s' smooth surface extension III.l'I'he stem III vis rotatably supported in a socket III having the.bifurcated end embracing the web of shoe l2l. Springs ill and Ill areattached to the shoes and to" the lanchor plate -Ill to hold the shoesin their brake released position. It .will be un'- derstood thatlthershoes are expanded by means part of .the Vforce so applied buifsincethe force so at. their opposite pair. o adiacent ends as in port of theforce which is applied to shoe 2| 65 when supplemented by the`self-energizing force applied by the drum to shoe 2i ,causes the braking eiiect of the two shoes to be substantially equal. In this way thewhole drum are is used and-the required pedal pressure is reduced to aminimum. In the case of reversedrum' rotation the effect issubstantially thesame. A part of J the pressure of the energized shoev2i is anchored isa-short distancetous.wf..A

Figure 1. In this form of the invention, counter'ciockwise drum rotationcauses the dium to supplement the pressure applied to shoe ill. 'I'heforce derived from ythe wheel cylinder and the self-energizationisltransmitted by the shoe in part to the abutment l!! and in part istransmitted to the secondary shoe through `theinstrumentality of thelink i, mitted to the secondary shoe is supplemented'by theself-energizing eiIect of the drum, the secondary shoe anchoring as inFigure l at the end of the wheel cylinder or upon some other' convenientanchorage, and using preferably the wellknown articulating Thus by theuse of VThe force transdate themselves to the outline of the drumexerting a maximum force at the mid-points of theirl arcs. the presenceof the anchorage for each and the 4resistance offered to drum rotationis substantially the same in the case of each shoe, this beingaccomplished by properly determining the lengths of the arms of lever|21. Upon reverse rotation of the drum the brake operates insubstantially the same way. It will be seen that this embodiment of theinvention so spaces the iulc'ra |23 and |26 that it becomes unnecessaryto resort to the expedient shown by'Figure i where the ends. of pin 1|are overlapped by the articulating links 2l, Il'. 'Ihe construction isthus greatly simplified.

Also each shoe is self-energizing due to" Figures-,.9 and 1o snow asimuarbut slightly different form. In this embodiment numeral ry,21| isused to designate the drum and k212 the cover. 'I'he anchor plate ismade up of two laminae 2N, 2li' in close contact with each other in theregion where they are secured tothe cover but spaced at the lower end ofthe drum where they straddle the lever 2I1. A spacer 2|9 is secured byfastening means 22 between the extremities of plates 2id and 2|5' andthis spacer is formed with an elongated slot 222 which receives the endof lever-2H. At its upper end thedever has an elongated slot 225embracing a pin 221 supported by the laminae 2|5, 2|5'. The lever 211 isformed on its opposite faces with recesses, one near the lower end andthe other near the upper end. The recesses receive the ends ofadjustable links 222 and 22| connested to the shoes 2,22 and 2li.springs 221, 222 connect the shoes to the anchor plate and bias theparts tothe position shown in Figure 9. Esch articulating link iscomposed of three parts, a shoe engaging Dart 24| having a biiurcatedend and a pivot pin 243. a stem 2l! hav- .ing one end unthreaded andreceived within a pocket of part 24| and a lthreaded end adjustsblyreceived with the third part, a socket .2, *which is seated. as 'statedabove. in a recess of the lever. The operation of the parts describedwill be understood from the description of the embodiment illustrated inFigure '1.

It will be observed that in Figure 9 there ls an adjustment in each ofthe shoe articulating links 229 and 23|, this arrangement diiering fromthe embodiment shown in Figure 'I in which but one of the articulatinglinks is made adjustable. 4When the articulating link for one shoe onlyis adustable a second 'adjustment is provided for the other shoe at itsend remote from the adjustment for the nrst shoe.' This construction isshown in Figure 1, the second adjust- 'ment being seen at 32. Theconstruction shown by Figure 9 provides another use for the laminatedanchor plate. Where. as in Figure 1, the

ends of the `wheel cylinder take the brake torquef the cylinder mustnecessarily be quite rigid. It is possible to make a wheel cylinder oflsheet metal insofar as its hinction of applying the brake is concerned,especialiy in a brake where the applied force may be low as in thepresent brake where self-energization is` used to supplement the appliedforce.

In Figures 11 and l2 there has sheet metal wheel cylinder to ser with ananchorageior the shoes inrispende t ci the cylindex'. The anchorage isin he s. pin 251 een shown a carried by the spaced upper ends 253 25T-ofthe anchor plates. By this construction the thrust of one or the otherof the brake shoes is transmitted directly to the pin 25| and is nottransmitted to the ends of the cylinder. It is therefore possible tomake the cylinder of light weight material. Inasmuch as the cylinderdoes 4not receive the brake torque a simplified form for its support ismade possible. The plates 253 and 253' are cut out as at 255 andoneither side of the opening so formed the plates are bowed away fromeach other to form cooperating pockets 251 and 25| within which thesheet metal cylinder 26| is mounted. This cylinder carries pistons 263and plungers 265 as before.

Within the opening 255 the cylinder is embraced by a block 251.A Theblock has an opening 269 registering with an opening in the cylinder andalso communicating with a conduit 21| from the master cylinder. A bleedplug is shown at 212. The pin 25| is formed with an axial extension 216to which the ends of springs 215' and 211 are connected, the other endsof these springs being connected to the shoes. By this means the shoes219 and 28| are normally heldin contact with the anchor pin' 25 I. Whilethis arrangement for supporting the cylinder and providing the adjacentanchor pin for the shoes may be used with other arrangements at theopposite ends of the shoes it is particularly useful with an arrangementcorresponding to that of Figure 9 since that, form makes use of atwo-part anchor plate.

I claim: f 1. In a brake. a drum, a pair of shoes friction- -ally toengage the drum. spreading means beact as a servo device to actuate theother shoe,

said mechanism comprising a lever positioned between the second pair ofadjacent ends. two pivot members about either of which said lever mayrotate. a link pivoted to each shoe, said links engaging said lever. onenear each pivot member and at a distance from the axis oi said pivotmember less than the radius thereof.

2. In a brake. a drum, a pair of shoes, a tlxed anchorage spreadingmeans between one pair of shoe ends, said anchorage having radiallyspaced slots, first and second pins in said slots, a lever includingfirst links rotatably mounted on said pins, one on each side of theanchorage. second links overlying said iir'st links and the ends of oneof said pins, said second links being rotatably supported on reducedends of the other of said pins,.other pin and slot connections betweensaid rst and second links andthe anchorage, said Second links havingoppositely directed slots between said flrst and second pins, andarticulating links pivoted to said shoes and engaging in said f slots. o

with retainer links mounted .alongside sec-.

ond links vto close the siete therein.

